…I was fortunate enough to find myself last week in Geneva, at CERN, the home of the Large Hadron Collider, watching the experimental physicists there announce the discovery of the Higgs Boson – or at least something very much like it. We think it is the Higgs Boson but we need more work to tell us that it is exactly that. It is certainly very HB-like. It was an absolute pleasure to be at a place where you knew history was being made. One way of saying the level of historical importance is that after thousands of years, the easy part is now over. It is as if you are watching people playing chess or some complicated game like Australian Rules football and we finally figure out what the rules are. Now the next step is to be good at playing chess.

So my talk to you is not going to be about particle physics per se, but the hard part of understanding the universe, what it means to be a human that is fundamentally – can be thought of as- governed by the laws of physics. So let’s start with epistemology (we always like philosophy lectures at our TAM meetings). How do we know what we think we know about how the world works?

So – you are outside on a beautiful night admiring the moon with a prospective romantic entanglement and you say isn’t it wonderful that we have this satellite that orbits us and has a metal core and a rocky coat. And your friend says well, I’ve always been partial to the green cheese hypothesis – the moon is green cheese. And you say well, we’ve been to the moon, brought bits of it back and it looks like it’s made of rock, not cheese. And your friend says well, there’s about ten metres of rock on top of green cheese. And you say well, we know enough about the moon’s density and rotation and so forth and it matches what you would expect for rock and metal and things like that. And your friend says well, you wouldn’t expect the moon’s green cheese to be just like regular cheese. This cheese does exactly that! So what can you do in this case where your friend is being a little overly sceptical? How do you escape the threat of the nihilism that it is impossible to know things? You are allowed to say that what you are saying is crazy, absurd. The only thing is, you need to be able to back this up, say why it’s crazy to say the moon is made of green cheese. It’s not just because we’ve been to the moon and analysed its spectroscopy. It’s because it’s embedded in a larger context.

We know something about the solar system and how it was formed. We know what moons and planets are. We know what cheese is and it’s a dairy product…. it does not give rise to things like the moon! After thousands of years, we now know at the most fundamental level how the world works.

• We now know the way the world works, in quantum field theory (QFT). Particles = fermion fields. Forces = boson fields.

• The universe consists of fields. Particles are what you see when you look at fields. There is absolutely no evidence that this is in any way incorrect. This has incredible implications for how we look at the world.

• QFT lets us delineate the scope of our understanding. There are no known unknowns in QFT. Ken Wilson (Nobel prize 1982) taught us that at the length of 1cm and above you don’t need to know what happens at shorter length scales. All of everyday life consists of three particles – electrons, protons and neutrons – interacting via three forces – gravity, electromagnetism and the nuclear force.

• Electrons in orbitals are bound to nucleus by electromagnetism. Protons and neutrons in nucleus are held together by nuclear force. Gravity pulls everything towards everything else.

• When I wave my hand or speak words this is all interaction, through electromagnetism mainly, all in accordance with the laws of physics.

• There is nothing else we need, or will ever need in a million years from now, to understand what is going on in the room right now. (This doesn’t get nearly as much publicity as it should – till right now!) You, a sceptic, may ask: How do you know there are no other new relevant particles in the world? Could there be new relevant particles? No.

• (Explanation in terms of Feynman diagrams) There are other particles – dark matter for example but dark mater doesn’t interact very strongly with us. If there were any new relevant particles, we would have produced them already. We have not done so. Could there be new relevant forces? No.

• QFT lets you ask that question qualitatively. They would have range, things coupled to them and strength.

• We know what the particles are, so we can look for new forces between them. There aren’t any.

• On a scale of less than 1cm, any new forces would be less than one hundred thousandth the strength of the force of gravity i.e. completely irrelevant for everyday life. Conclusion: When it comes to the laws of physics underlying everyday life – baseball, tables, viruses, human beings – we are done. We don’t need to say that physics is finished. Not even close. There is plenty we don’t understand:

• complicated systems- turbulent weather, high temperature super-conductivity, cancer, consciousness, economics… However, we don’t need to understand these things to understand what is going on in the room, how human beings work as physical systems. Just because we know how the horsey thing moves across the board doesn’t make us a great chess player. But when planning how to play chess, it’s best to know you can’t move the horsey thing diagonally. Sensible answers to questions in economics, for example, have to be compatible with what we know about fundamental physics. What we know about fundamental physics has consequences. The way the world works has consequences -simple and profound:

1.No astrology, no homeopathy, no spoon-bending. With all due respect to James Randi and others who debunk claims of paranormal powers, we already know in advance that what is claimed (claims that not compatible with the fundamental laws of physics as we know them) can’t be right. You can’t bend spoons with the force of your mind because there are no forces of nature that allow you to do that. The electromagnetic force comes closest but you could test easily for this with iron filings. No force can extend from stars and planets to my little birthplace. Of course it is possible that this one person has the capacity to violate the fundamental LOP. In the same way that it is possible that the moon is made of green cheese. But if you believe the moon is not made of green cheese, you should also believe the standard model in physics and its consequences.

2. The next consequence is a little bit bigger. There is no life after death. Because there are no particles or forces that could contain the information in your brain after you die. There is no way for that knowledge of who you were before you died to persist after you’ve died, after the chemical reactions that define your life come to an end. I am talking about some extra-material spirit that would somehow be you after you cease to exist. That is not compatible with the laws of physics. We don’t need to look at past-life regression studies or anything like that. The claim violates the laws of physics.

3. There is no ghost in the machine; no extra-physical volition. What you are is a collection of atoms obeying the laws of nature. You are not a physical meat sack that is being driven a round by a little blob of spirit energy (like a soccer-mom driving an SUV). There is no extra- material spirit: there are electrons, neutrons and protons interacting through the nuclear, electromagnetic forces and gravity. Not necessary to bring anything else into the equation.

4. Finally, there are no externally served purposes or morals. If you know exactly the state of the universe at any moment in time and had the computational power, then you could predict what is going to happen in the future and retrodict what has happened in the past. This is absolutely implausible at a practical level – it will never ever happen – not even worth thinking about. What it means is that the laws of physics are not teleological – they do not tend towards a goal. The laws of physics do not care what you do. They do not judge you. The laws of physics just happen over and over again. Figuring out how to act in a world that obeys the laws of physics is the hard part. Q. If physics fixes what the world is, what else is there? (It will take hundreds of thousands of years to figure out what it means to have a good and fulfilling life. But whatever it is, it has to be compatible with the laws of physics at a fundamental level). A. How we talk about the world. E.g when on a first date and someone asks you to talk about yourself you do not answer in terms of particles, positions and velocities etc. Not plausible, feasible, useful. You would describe yourself in more coarse-grained terms. You’d use another vocabulary, not use the word atom at all. You would tell some story of who you were. All the freedom to bring meaning and purpose and right and wrong into the world inheres in that ability to tell different stories about the world:

• ‘The world is made of stories, not of atoms’ Muriel Rukeyser. We access and confront the world via higher level models/theories/ontologies/ vocabularies / stories.

• The world is also made of atoms. It depends on what sort of story you want to tell about the world. We bring reality to life by talking about it in different ways.

• The freedom to do this makes the universe what it is for us. (Stories are not fictional but true stories) • Example of overlapping stories in fluid mechanics and thermodynamics: Story 1: atoms, molecules with certain positions and velocities Story 2: a fluid with temperature, pressure, velocity etc.

• There is no analogue at the level of atoms and molecules. They are different ways of describing the world. This is what we have in mind when talking about values etc. • Values (purpose, meaning, morals) only appear in higher level stories. Not part of QFT. How do we choose which values to hold?

• Not fixed by the laws of physics. Human beings are not blank states.

• We have goals, aspirations, desires feelings.

• We choose to tell stories that 1. Are compatible with how the world works and 2. Help us fulfil our desires, reach our goals.

• For example, should we let same sex couples get married? One way would be to say there is a natural way. I would say this is a mistake – an incorrect way of thinking about our world. Our world does not have natural ways to be. We invent right and wrong ways. Two fundamental views on gay marriage:

• There is a ‘natural’ and correct way for humans to live. This is the natural and correct form of marriage – one man, one woman.

• How to live is a decision we humans have to make. No configuration is naturally correct. We decide how to best guarantee happiness and protect individual dignity. I’m not saying you can’t decide it’s not good to have gay marriage but the chances are if you realise there is no ‘natural’ God-given way then you’ll come down on the other side of allowing gay people who are in love to marry each other (applause). To end, picture us from Voyager. We are very small. Hubble ultra-deep-field. Empty sky. 1oo billion stars in our galaxy. 100 billion galaxies. Despite the fact that we are small. We have figured this out. We have taken the first steps, knowing the rules of the game. Now how to play the game well? End

by Sean Carrol

From Particles to People was last modified: April 30th, 2018 by WebTeam